Adams, James Truslow, author
1946
Buku Referensi
editor Thomas C. Cochran, Wayne Andrew
Charles Scribner's Sons , 1962
Buku Referensi
Dull, Jonathan R
Yale University Press, 1985
Buku Teks
rand McNally and Company, 2003
Buku Teks
Muccigrosso, author
Krieger publishing company, 2001
Buku Teks